Some rocks according to their use or texture are classified into different types. Know more about Conglomerate Texture and Chalk Texture. The types of Conglomerate and Chalk are Not Available.During historic times, some rocks depending on their hardness were used to create Pictographs and Petroglyphs. Rocks which are hard were generally not used. Pictographs are paintings or drawings that have been placed or created on the surface of rock. Conglomerate and Chalk were used for creating pictographs. Petroglyph is an image which is carved into a rock. These are images created by removing part of a rock surface by incising, picking, carving or abrading, as a form of rock art. Conglomerate and Chalk were used for creating petroglyphs.